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Light Weight High Gain High Data Rate Launch Vehicle Antenna


OBJECTIVE: Investigate alternative SATCOM links and develop novel high bandwidth, high gain antenna designs to achieve higher data rates for the link between the EELV booster and the GIG as it traverses from the launch pad to the end of powered flight. DESCRIPTION: Evolved Expendable Launch Vehicles (EELV's) have a requirement to monitor the upper stages during orbit insertion and disposal in order to detect and recover from anomalies observed in flight. Video monitoring of the flight is desirable and requires data rates of 10-20 Mbps. Existing EELV antennas can support the required data rates while within line-of-sight (LOS) of the ground terminal, but when the vehicle leaves LOS it converts to a satellite communications (SATCOM) data link with a lower data rate that does not support the desired video monitoring of the flight. The existing EELV antennas use a Tracking and Data Relay Satellite (TDRS) S-band link, which limits data rates to<400 kpbs, but there may be alternative SATCOM links at other frequencies that are available for future use and that can support higher data rates. Some potential SATCOM data links have been identified in previous studies, but a thorough evaluation of the alternative SATCOM links is needed to assess their availability and performance. Examples of alternative SATCOM links include Iridium and Inmarsat at L-band frequencies and the TDRS Ku- and Ka-band links. In addition to identifying alternative SATCOM links, new high-gain, high bandwidth antenna designs and architectures are needed. These antennas must support 10-20 Mbps data rates over the selected SATCOM link, with near-hemispherical coverage from launch to end of powered flight. A comprehensive trade-off study of the possible data links and their impact on antenna design/performance (gain requirement, coverage requirement, polarization requirement, etc.) should be a key technical task for Phase I. New designs must also meet the physical limitations surrounding launch vehicle external telemetry antennas. Antenna height above the launch vehicle surface (a function of aeroheating) and depth behind the skin of the vehicle (due to impacts on internal structures), as well as surface area (antenna aperture) are a few of the more important physical concerns when considering a launch vehicle antenna and will often determine where an antenna may be mounted. There are, of course, other environmental requirements (shock, vibration, etc.) as well as electrical requirements (power handling, coupling, etc.) that further define the antenna attributes. The antenna must meet the size, weight and power (SWaP) constraints of EELV"s, using the existing power supplies and without significant changes to the footprint of the antenna on the launch vehicle. The specific physical, environmental and electrical requirements should be explored and identified in the Phase I effort and be used to constrain the antenna design. PHASE I: Investigate alternative SATCOM links that can be used to support high data rates. Perform a trade-off study to select the best data link. Develop a preliminary antenna design utilizing the selected data link and meeting the identified physical, environmental and electrical constraints. Demonstrate through simulation and analysis that the antenna concept can support the required data rates. PHASE II: Fabricate a prototype antenna based on the results at the conclusion of Phase I. Characterize the antenna through comprehensive S-parameter and gain measurements. Use measured data to predict the system level performance, including a full link analysis. Use a combination of testing and analysis to evaluate antenna performance under realistic launch vehicle environmental conditions. PHASE III: Military Application: EELV telemetry antennas and other future follow-ons to EELV. Commercial Application: With commercialization of the space program, newly developed commercial launch vehicles will require similar technology for telemetry antennas. REFERENCES: 1. Welch B and Greenfeld I,"Launch Vehicle Communications,"NASA/TM-2005-213418, published by National Aeronautics and Space Administration, Glenn Research Center, Cleveland, OH, Jan 2005. 2. Whiteman D, Valencia L, and Birr R,"Space-Based Telemetry and Range Safety Project Ku- and Ka-Band Phased Array Antenna,"NASA/TM-2005-212872, published by National Aeronautics and Space Administration, Dryden Flight Research Center, Edwards, CA, July 2005. 3. Range Commanders Council Telemetry Group,"Telemetry (TM) Systems Radio Frequency (RF) Handbook,"RCC Document 120-08, published by the Secretariat, Range Commanders Council, US Army White Sands Missile Range, New Mexico, March 2008.
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